In a semiconductor device, an integrated circuit is becoming highly integrated. In a DRAM, it is required that the area of a memory cell is made small and the storage capacity is made large. To comply with this requirement, a capacitor having a structure of MIM (metal-insulator-metal) is getting a lot of attention. In the capacitor of the MIM structure, a material having a high dielectric constant such as tantalum oxide (Ta2O5), strontium titanate (SrTiO) or the like is used as an insulation film (dielectric film).
Where an oxide-based material having a high dielectric constant is used as a dielectric film, a necessary dielectric constant is obtained by performing a post-treatment such as a heat treatment or a UV treatment. At this time, the post-treatment is usually performed in an oxygen-existing atmosphere in order to prevent oxygen from escaping from the oxide material. Thus, attention is paid to ruthenium which is more difficult to oxidize than polysilicon which is conventionally used as an electrode material.
In the meantime, the shape of a capacitor is formed into a cylindrical or laminated electrode structure in order to increase the storage capacity of a DRAM. In this structure, it is necessary to form an electrode in a state in which a large step is formed. For that reason, a good step coverage property (step covering property) is required in forming a film. Thus, a CVD (Chemical Vapor deposition) method, which is essentially high in step coverage, is used as an electrode formation method. Furthermore, an ALD (Atomic Layer Deposition) method, which is one type of CVD method, in which a precursor and a reducing gas are supplied alternately, is taken into account.
As a technology of forming a ruthenium film with a CVD method, there is known a technology in which a ruthenium film is formed by adding an oxygen gas to a ruthenium compound having a structure in which two β-diketones and two groups selected from olefin, amine, nitrile and carbonyl are coordinated in Ru and consequently decomposing the raw materials on a heated substrate.
However, it is hard to obtain sufficient step coverage using the aforementioned technology. If an ALD method is used, it is possible to improve the step coverage. However, the throughput becomes extremely low.